A user equipment detects a downlink control channel (e.g., PDCCH (physical downlink control channel)) carrying scheduling information on downlink data transmission and may be then able to receive downlink data from a base station. In a legacy wireless communication system, a position of a downlink resource to which the downlink control channel is mapped can be inferred from different control information (e.g., CFI (control format indicator)). Hence, a user equipment can monitor the downlink control channel on the position of the downlink resource. And, a legacy downlink control channel can be demodulated based on a channel, which is estimated based on a cell-specifically transmitted reference signal.
Meanwhile, an enhanced physical downlink control channel (e.g., EPDCCH (enhanced PDCCH)) can be used in an improved wireless communication system. The EPDCCH is configured to be transmitted in a resource position differentiated from a resource position in which PDCCH is transmitted and the EPDCCH can be transmitted based on a DM RS (demodulation reference signal) instead of a cell-specific reference signal.
A user equipment operating in an improved wireless communication system can received both PDCCH and EPDCCH. To this end, it is necessary to provide the user equipment with information on a downlink control channel (PDCCH or EPDCCH), which is monitored by the user equipment in a downlink subframe. In case of monitoring EPDCCH, it is necessary to provide the user equipment with information on a resource position used for monitoring the EPDCCH. Moreover, in case of monitoring EPDCCH, it is necessary to clearly determine whether the user equipment monitors a physical HARQ (hybrid automatic repeat request) indicator channel (PHICH) which is transmitted in a PDCCH mapping area.
According to operations of a currently defined wireless communication system, it is necessary to have a method of efficiently configuring a type of a downlink control channel monitored by a user equipment and information on a resource position to which a downlink control channel is mapped in a manner of combining the type and the information with each other. And, when a user equipment monitors EPDCCH, it is necessary to have a method of clearly determining whether the user equipment monitors PHICH.